[Antennas]

I was cutting a VW logo as practice and it was not bad but on the final pass around the outside it cut it way off. SO I cut it again and same thing even worse. So I figured I'd cut some circles to see, they cut fine. I cut 3 circles inside one another at a very small depth. But I measured them and they are fine.

Why would it not cut the logo right but the circles fine??

Even on the last VW cut in MDF at a very shallow depth it was off slightly at the top right and bottom left areas, as the width doesn't match.


Any ideas??
Thanks.

[ger21]

Could be quite a few different things. The really bad ones look like it's losing steps. The better ones could be due to flexing of the machine, or it could be lost steps as well.

[atwooddon]

Was the VW logo from a nc file you generated? If so, did you draw it in a CAD program? The reason I ask is the circles not being round are not the only issues. Edges that should be straight are showing some uneven cuts also. Look at some of the edges in the 'VW' part of the logo, they are not all straight. My guess is either missing steps or the machine is flexing tho it shouldn't be having addln flexing while cutting a straight edge, that should be a constant load on the structure. See attached pictures, white arrows pointing at other uneven cuts.

Don

[Orion13]

You built your machine from buildyourcnc website if I remember correctly. Did you use the design of a single stepper on the Y axis with shafts out either side and sprockets on the ends? If so I can tell you from experience that you can and will get slippage from the sprockets if you don't put a flat spot on the shafts for BOTH axle locks to bite onto. I had this exact same thing with circles happen to my machine and I had to take the Y apart and grind two sides of that shaft to get the contact needed to keep if from slipping. Just a thought on where to look with that style of machine. Hope you find your issue if this isn't your problem.

Orion

[Antennas]

Thanks everyone I meant to reply earlier but got busy. Thank you for your help.

Sent from my SGH-I317M using Tapatalk

[louieatienza]

Was the VW logo from a nc file you generated? If so, did you draw it in a CAD program? The reason I ask is the circles not being round are not the only issues. Edges that should be straight are showing some uneven cuts also. Look at some of the edges in the 'VW' part of the logo, they are not all straight. My guess is either missing steps or the machine is flexing tho it shouldn't be having addln flexing while cutting a straight edge, that should be a constant load on the structure. See attached pictures, white arrows pointing at other uneven cuts.

Don

I'd agree that there is flex going on and the most apparant spots you'll see them in circles or curves is at diagonals to the axis movement. I think the spots you marked may just be the entry/exit points of the tool. Basically, in my opinion, there seems to be flex or looseness everywhere - the drive mechanisms, and linear bearings, and possibly the machine itself.